Metal Tube Rotameter-FAQ

The metal tube rotameter is an instrument for the measurement of flow rate in liquids and gasses.  It operates on the basic principle of the variable area. It consists of a tapered steel tube with a ‘float.’ The metal design body of the instrument makes it a durable and robust instrument.

In this FAQ guide, we will answer some basic metal tube rotameter questions. You will hopefully be able to understand the functioning and applications of metal tube rotameters. In addition, we will cover the metal tube rotameter functions, specifications, applications, operating principles, and related terminologies.

1. What is a metal tube rotameter?

Metal tube rotameter is a variable area flowmeter that measures the spontaneous flow rate of liquids, gases, and steam applications. A metal tube rotameter is suitable where a normal rotameter cannot withstand demanding pressure and temperature constraints. Metal tube rotameter is best for measuring opaque fluids under high pressure and temperature.

Metal tube rotameter can measure the liquid and gases of density up to 2.95. The temperature range is up to 400°C, and the design pressure range of up t0 25 kg/cm² and has a measuring range of 100 to 40,000 LPH of water/Liquid 3.3 to 1400 Nm³.

2. How does it work?

The metal tube rotameter works on the variable area principle, in which the fluid increases the float in the tapered tube and increases the area of the fluid passage. The float moves through the linkages and counterweight. The float moves through the tapered tube upward and downward with the movement of fluid flow. The tube and float combination determines the flow rate.

There is a high magnetic field detections sensor that detects the inner float magnetic field. The metal tube rotameter does not need any electrical connection as it operates on a battery and has a built-in two-wire transmitter that takes 4 -20 ma signals.

3. What are the specifications of the metal tube rotameter?

Metal tube rotameter measures the flow of liquid and gas under critical conditions. It consists of a tapered tube, assembly, float, and rotating magnets that connect with the pointer. The movement of the float is measured in terms of flow rate. It has the material of SS316, SS316L, SS304, and titanium. It has the protection class IP-65 and IP-66. Also, you can customize the protection on request.

The metal tube rotameter has a repeatability of 0.5% and a scale length of 90°angular. It offers the accuracy range of ±2% of total flow, ±1.5% of full flow (optional), or customizes the better accuracy for your application. The fluid temperature ranges from -20° to 100°.

4. What are the benefits of metal tube rotameter?

Metal tube rotameter offers many advantages to its users. The measuring part of the metal tube rotameter consists of a measuring tube and is afloat.  It is widely used in various applications because of its long measurement range, easy installation and maintenance, and low-pressure drop. It has high detection range and is suitable for medium flow measurement. As compared to the glass tube rotameters, they offer superior strength and durability.

The significant advantage of metal tube rotameter is its ability to measure high temperature and high-pressure fluids. The temperature range of up to 400°C, and the pressure is up to 70 MPa. The high-quality stainless steel material makes it anti-corrosive. Another advantage of the metal tube rotameter is that the loss of pressure is constant. The differential increases higher flow rates due to friction losses. The accuracy range of the metal tube rotameter is ±2% of full-scale reading, which improves with individual calibration. It has excellent repeatability.

5. What are the disadvantages of metal tube rotameter?

Although metal tube rotameter is suitable for many applications, it has certain drawbacks. Because of the reliance on fluid to displace the float, the metal tube rotameter can only be precise for a given substance at a specific temperature. In addition, floats are insensitive to viscosity, so different rotameters or scales should be used to measure densities and viscosities.

Metal tube rotameter has a relatively small size, not greater than 6 inches. For designs of larger pipes, it is inapplicable. It should be held upright; otherwise, a tilt can result in an inaccurate measurement. The direct flow indication of metal tube rotameter has a poor resolution as compared to other measurement principles. The reading of some fluid is obscure as the float must be read through the flowing medium.

6. What is the construction of the metal tube rotameter?

Metal tube rotameter has a long vertical tube with a transparent body to view the flow of fluid in it. The transparent tube is in a conical shape with measurement scales and floats. This tube helps in understand the measurements directly. Another part of the metal tube rotameter is the float that provides accurate dimensions within the tube. It also shows the flow rate in the tube. The float has the material of glass, plastic, or metal.

The scale indicates the float by showing the measurement of flow. Transmitter also plays a vital role in the construction of metal tube rotameter. It records the measurement accuracy and works with the electricity supply.

7. What are the preventive measures while using metal tube rotameter?

While using the metal tube rotameter, you have to take care of few things. First, since it has glass material, it must be handled carefully. Second, please do not set the flow meter to 0, instead set it to at least 0.5 liters per minute. Setting it to 0 can obscure the flow of pressurized air that can damage the metal tube rotameter. Next, clean the outer layer of glass using an alcohol swab.

The float can be stuck at the base of the rotameter that can block the flow of air, affecting the readings. To overcome this issue, invert the rotameter upside down to move the float from the base. You can also use the wind to remove it.

8. What is the working principle of metal tube rotameter?

The metal tube rotameter measures the velocity of air and liquid. It has wide usage in various applications and medical instruments such as oxygen cylinders and anesthesia machines. The metal tube rotameter consists of an outer vertical glass tube with a broad top and narrow base. It is also known as a variable area flowmeter because of the variation in the cross-sectional area of the tube. There is a metering float inside the tube, and three forces act on it, weight, blow force, and buoyancy.

The float rises with a rise in fluid pressure. As the glass tube is broad from the top, the upward fluid escapes from the sideways. So, even at high fluid pressures, the variable drags force to its initial state.  The system reaches the equilibrium state when the upward force balances the weight of the float. The glass tube can be labeled from 1 to 12 to indicate the flow rate of the gas.

9. What are the applications of metal tube rotameter?

Metal tube rotameter is generally made of aluminum, stainless steel, or brass. It is ideal for high temperatures and pressure and has high corrosion resistance properties, used for corrosive liquids that cannot be suitable for glass tube rotameter. The fluid ideal for measuring metal tube rotameter includes hot water, hydrofluoric acid, slurries, molten metals, etc. These fluids can operate at pressures up to 750 psi and temperature to 540°C.

Metal tube rotameter has digital control and acts as a flow transmitter. The metal coupling detects the float position. Some of the metal tube transmitters have alarms for measuring the fluid flow. Two floats can be used, one for volume and one for density. The metal tube rotameter is highly suitable for applications, including chemical injection, gas metering, high-pressure flow meters for oil platforms, and measurement of liquids, gasses, and oils.

Because of its reliability and efficient services, the metal tube rotameter has grown in petrochemical, metallurgy, pharmaceutical, food, steel, and other industries. The metal tube rotameter is also applicable in gas seal monitoring for turbo compressors, emulsifiers, and lubricants.

10. What are the features of metal tube rotameter?

The metal tube rotameter has a dual-line LCD with a backlight. The magnetic coupling structure of the metal tube rotameter ensures a stable transmission signal. The metal tube rotameter is designed with different materials that can be applied for various media conditions. These rotameters can withstand the harsh environment and corrosive media. Also, it provides good heat and pressure resistance.

The metal tube rotameter is easy to maintain and install. The heavy-duty design of the metal tube rotameter provides maximum visibility. It ranges between 25 LPH to 60000 LPH, with an accuracy of ±2% of full scale. In addition, the metal tube rotameter prevents the low-temperature fluid from absorbing any heat.

11. What is the versatility of metal tube rotameter?

The metal tube rotameter is a versatile and accurate variable area flow meter that offers 2% full-scale accuracy.  It has a simple and easy-to-understand flow principle and is versatile for all types of fluids. While installing the metal tube rotameter, there is no configuration or calculation required. Instead, the scale indicates the flow rate with a needle pointed to the rotating float using a magnet.  The meter can output 4-20mA for flow rate, and that signal can be used to display the flow rate.

The metal tube rotameter can handle all types of liquids and gasses with high corrosive properties. Metal tube rotameter is an easy and simple measuring tool. It provides resistance against corrosion, abrasion, and shocks, with little and no maintenance requirement.

12. What are the performance characteristics of metal tube rotameter?

In a metal tube rotameter, the flow rate is proportional to the area. Most of these rotameters have equal-scale increments and are nonlinear by about 5%. Therefore, the metal tube rotameter is suitable for low-flow rates. Its full-scale capacities range from 0.5cm3/min of water and 30 std cm3/min of air in over 1200 liters of water.

You can install the metal tube rotameter without any fitting or lengths of straight pipes. As a result, the metal tube rotameter is a reliable instrument used commonly in industrial automation process control. In addition, the high detection range of these rotameters makes them very convenient to use.

The metal tube rotameter changes with viscosity changes. Smaller rotameters are more sensitive than larger ones. You can determine the viscosity limit by material and float shape. The metal tube rotameters are also dependent on the density.

13. How is the metal tube rotameter better than the glass rotameter?

Metal tube rotameter offers many benefits to its user as compared to the glass rotameter. Metal tube rotameter can withstand high pressure and temperature with high mechanical strength and durability. In these rotameters, there is no need for straight pipe upstream. The metal tube rotameter is easy to install and replace at an affordable cost. It is chemical, and pressure compatibility makes it applicable for various purposes.

Metal tube rotameter has gain popularity because of their simple structure and high reliability. Over the years, many new and advanced technology meters have been introduced, but metal tube rotameter is still popular among users. Unlike glass rotameter, its metal construction makes it strong and stable. The new magnetic coupling structure of the metal tube rotameter ensures stable signal transmission. In addition, the metal tube rotameter can withstand the harsh environment and corrosive media.

14. What to calibrate metal tube rotameter?

The metal tube rotameter is a flow measurement device. The indicator floats at a steady value, while the weight of the float and fluid acts as the main forces. For calibrating metal tube rotameter, it should be done at the same temperature and pressure, with the same density of the gas. You should calibrate the actual gas, but some gases such as oxygen and carbon monoxide cannot be used because of their toxic properties.

A metal tube rotameter can measure one specific gas density and flow range. If you do not calibrate with these conditions in mind, accuracy can suffer. In addition, you need to calibrate the design regulators to reduce the higher supply pressure to lower test pressure. A fast-reacting temperature measurement device is favorable for initial calibration.

For pressure measuring, a digital pressure gauge or a lab barometer is recommended. For temperature and pressure measurement, digital instruments can be interfaced with data collection. The level of the metal tube rotameter must be perpendicular to achieve the best results. In addition, the float should be kept in a constant balance with the flow; otherwise, it can cause inaccuracies.

15. How to calibrate the metal tube rotameter?

You have to follow some steps for calibration of the metal tube rotameter. The first step is to start the gas flow by beginning at the highest flow and working down. Next, adjust the flow control and allow time for flow, pressure, and temperature stabilization. Record the indication of the metal tube rotameter, the gas pressure, and temperature, convert this into the mass flow, and apply square root density correction.

For getting the accurate calibration, leave the metal tube rotameter indication uncorrected. It will keep the metal tube rotameter at the cardinal point. For calibration of the metal tube rotameter for different gas, the results will not be the same.

16. What are the components of a metal tube rotameter?

The metal tube rotameter consists of metering tubes that avoid internal stresses. The tubes are formatted with reproducibility and with various shapes. The non-conical tubes can extend the graduations at the lower end of the range. The floats are comprised of multiple materials that provide resistance to corrosion and have stainless steel bodies.

The metal tube rotameter adopts the principle of variable area flowmeter. Therefore, the floater can move freely in the taper measuring pipe—the position of the floater changes with the flow changes. As the metal tube material cannot make the readings visible, the float position is transmitted to magnetic coupling from where the readings can be read.

17. How to choose the right metal tube rotameter for your application?

Metal tube rotameter has a different application than the glass tube application. It can measure high temperature and pressure, and tubes have aluminum, brass, or stainless steel. From the metal metering tube, the piston position can be decided. While selecting the metal tube rotameter, make sure to know the specifications of your metal tube rotameter so that you can choose the right one for your application.

If you are looking for corrosion resistance material, a metal tube rotameter is the best option. Also, if you measure abrasive liquids and there is a risk of damage to metering tubes, use a metal tube rotameter. They offer impact strength at a low cost.

18. What is a horizontal display metal tube rotameter?

The horizontal metal tube rotameter is suitable for horizontal pipe installation. It has a magnetic sensor, a high-performance MCU. It features high and low limit alarm function and signals transmission with high precision and reliability with a simple structure, easy installation, and reliability. These horizontal metal tube rotameter are applicable for all kinds of media environments, such as corrosive or explosive ones.

They are suitable for small and medium flow measurement in small or medium pipe diameter. Horizontal display metal tube rotameter is widely used in various industries, including food, metallurgical industry, pharmaceutical, chemical, etc.

19. What to do when troubleshooting metal tube rotameter?

When you are using a metal tube rotameter, sometimes issues happen with the float. For example, the pointer of the rotameter vibrates, so it results in inaccurate measurements. If there is the normal flow of liquid in the pipeline but only the vibration of the metal tube rotameter, it means there is a problem with the float. The most common reason is that the float gets stained with dirt and impurities. You can resolve this issue on your own rather than taking help from the operator.

You need to stop the operation and then remove the impurities on the float and tube. So whenever there is a minor issue of pointer vibration, it’s simple to resolve. The problems with the metal tube rotameter also arise because of corrosive environment or alkaline gas. Rust can also damage metal products. Corrosion and rust can affect the product’s service life if you do not deal with it timely. You can take out the rust by using a cleaning agent.

20. How to resolve float stuck in metal tube rotameter?

The main issue with the metal tube rotameter happens because of the float. If the float does not move, the magnetic steel and the pointer of the metal tube rotameter will not move as well. Therefore, if you handle metal tube rotameter carelessly, it can damage the accuracy of measurements. Sometimes, the quick opening and closing of the valve can put excessive pressure on the rotameter. Due to this, the float and pointer cannot move.

If the medium in the metal tube rotameter has iron chips, it can damage the magnetic steel of the float. The float can absorb the iron chips and can get stuck. The float in the metal tube rotameter has specific gravity because of the vertical installation. If there is minimum medium pressure, the float cannot lift, and a pointer cannot move with the float. The diameter of the pipe has the upper and lower limit of measurement. If the upper limit does not reach the lower limit of the rotameter, the pointer will not move.

Conclusion

Instruthinkoffers a range of metal tube rotameters to our customers for various flow measuring applications. Our high-quality and durable metal tube rotameter is a convenient measuring instrument to monitor the flow rate. Our products are manufactured and inspected under technical expertise that ensures the safety and durability of our products.

So, have any concerns/ queries about the metal tube rotameter, you can discuss your inquiries with our team at sales@instruthink.com or directly call us on +44 7700 307784.